3229-70-7Relevant articles and documents
The rate of excited-state proton transfer to solvent from trifluoromethylphenols in water
Kaneko, Shigeo,Yoshihara, Toshitada,Tobita, Seiji
, p. 312 - 313 (2009)
The proton-transfer reactions to solvent from electronically excited o-, m-, and p-(trifluoromethyl)phenols (TFOHs) in water have been investigated by picosecond time-resolved fluorescence measurements. The rate constants for the proton dissociation of o-, m-, and p-TFOH are obtained to be 2.2 × 10 9, 8.6 × 108, and 2.5 × 108 s -1, respectively. On the basis of the rate constants, the effects of substituent and deuterium isotope effects on the proton-transfer reactions are revealed. copyright
Alkali and alkaline-earth metal ion catalysis in the reaction of aryl acetates with methoxide ion. Effect of a poly(oxyethylene) side arm
Ercolani,Mandolini
, p. 423 - 427 (1990)
The effect of added alkali (Na, K) and alkaline-earth (Sr, Ba) metal bromides on the rate of acyl transfer from o-acetoxyphenyl 3,6,9,12-tetraoxatridecyl ether (2) to methoxide ion in methanol at 25 °C has been investigated spectrophotometrically. All of the added salts increased significantly the rate of reaction in the order Na+ + 2+ 2+, a maximum catalytic effect of nearly 102 being observed with the latter metal ion. A proper analysis of rate data afforded equilibrium constants for associations of metal ions with reactants and transition state, showing that in all cases the transition state binds metal ions much more strongly than the reactants. An analogous set of rate measurements was carried out for comparison purposes on the corresponding reaction of phenyl acetate (1). The fact that catalytic effects are much greater with 2 than with 1 reveals that a substantial contribution to the stability of the transition state of the metal ion assisted path arises from interaction of the metal ion with the oxygen donors of the side arm.
Kinetics and Mechanism of the Aminolysis of Phenyl Thionoacetate in Aqueous Solution
Castro, Enrique A.,Ibanez, Fernando,Santos, Jose G.,Ureta, Carmen
, p. 4908 - 4912 (1993)
The reactions of a series of secondary alicyclic amines with the title substrate have been subjected to a kinetic study in water at 25 deg C, ionic strength 0.2 M.Pseudo-first-order rate coefficients (kobsd) are found throughout, under amine ex
CATALYSIS BY ALKALI AND ALKALINE-EARTH METAL IONS IN NUCLEOPHILIC ATTACK OF METHOXIDE ION ON CROWN ETHERS BEARING AN INTRA-ANNULAR ACETOXY GROUP
Cacciapaglia, Roberta,Lucente, Silvia,Mandolini, Luigi,van Doorn, Arie R.,Reinhoudt, David N.,et al
, p. 5293 - 5304 (1989)
Rates of reaction of methoxide ion with crown ethers bearing an intra-annular acetoxy group are markedly enhanced by alkali and alkali-earth metal bromides as a result of much stronger interactions of the metal ions with transition states than with reactants.
NEW INSIGHT INTO THE MECHANISMS OF REACTIONS BETWEEN SOME ANIONIC NUCLEOPHILES AND PHENYL ACETATE IN THE GAS PHASE
Kleingeld, Jan C.,Nibbering, Nico M.M.,Grabowski, Joseph J.,DePuy, Charles H.,Fukuda, Elaine K.,McIver, Robert T.
, p. 4755 - 4758 (1982)
Experiments carried out in an ion cyclotron resonance (ICR) drift cell, an ICR trapped ion cell and a flowing afterglow (FA) system show that in the gas phase phenyl acetate reacts with a variety of clustered and unclustered nucleophiles to yield mainly the product ion C6H5O-.
Gas-phase proton-transfer reactions between alkoxide anions
Dodd, James A.,Baer, Susan,Moylan, Christopher R.,Brauman, John I.
, p. 5942 - 5949 (1991)
Reaction efficiencies for proton transfer between alkoxide anions and neutral alcohols have been measured in an ion cyclotron resonance spectrometer, using a competition kinetics technique. The efficiencies for identity proton-transfer reactions are measurably less than 0.5, which is the simple statistical prediction for a thermoneutral reaction with no energetic barrier. In addition, the trend in reaction efficiencies for exothermic proton transfers is consistent with the presence of a substantial Marcus intrinsic barrier. An energetic barrier of this magnitude is not consistent with a surface which is believed to have little or no barrier. The results are consistent, however, with recent quasi-classical trajectory calculations which show that efficiencies for reactions on a barrierless surface can be slower than expected.
Kinetic Study on Nucleophilic Substitution Reactions of O-Phenyl O-Y-substituted-Phenyl Thionocarbonates with 1,8-Diazabicyclo[5.4.0]undec-7-ene in Acetonitrile
Um, Ik-Hwan,Park, Kyoung-Ho
, p. 1169 - 1173 (2017/09/13)
Second-order rate constants (kN) for nucleophilic substitution reactions of O-phenyl O-Y-substituted-phenyl thionocarbonates (4a–4k) with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in MeCN at 25.0 ± 0.1°C are reported. The reactivity of 4a–4k decreases as basicity of the leaving group increases except O-2,4-dinitrophenyl O-phenyl thionocarbonate (4a), which is less reactive than O-3,4-dinitrophenyl O-phenyl thionocarbonate (4b) although the former possesses 2 pKa units less basic nucleofuge than the latter. The Br?nsted-type plot for the reactions of 4b–4k is linear with βlg = ?0.50, a typical βlg value for reactions reported to proceed through a concerted mechanism. The Hammett plot correlated with σY? constants for the reactions of 4b–4k results in a better linear correlation than that correlated with σYo constants. Besides, the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρY = 2.12, r = 0.68 and R2 = 0.990, indicating that a negative charge develops partially on the O atom of the leaving group in the rate-determining step (RDS). Thus, the reactions have been concluded to proceed through a forced concerted mechanism. Effects of steric hindrance on reactivity and reaction mechanism are also discussed in detail.
Kinetic study on alkaline hydrolysis of Y-substituted phenyl picolinates: Effects of modification of nonleaving group from benzoyl to picolinyl on reactivity and reaction mechanism
Kim, Myung-Joo,Kim, Min-Young,Um, Ik-Hwan
, p. 1138 - 1142 (2015/07/15)
Second-order rate constants (kOH-) for alkaline hydrolysis of Y-substituted phenyl picolinates (6a-6i) have been measured spectrophotometrically. A linear Bronsted-type plot is obtained with βlg = -0.34, which is typical for reactions reported previously to proceed through a stepwise mechanism with formation of an addition intermediate being the rate-determining step (RDS). However, σYo constants result in a much poorer Hammett correlation than σY- constants. Furthermore, the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρY = 0.82 and r = 0.72, indicating that a negative charge develops partially on the O atom of the leaving group in the RDS. Thus, the reactions have been concluded to proceed through a forced concerted mechanism with a highly unstable intermediate 7. Comparison of the current kinetic data with those reported previously for the corresponding reactions of Y-substituted phenyl benzoates has revealed that modification of the nonleaving group from benzoyl to picolinyl causes not only an increase in reactivity but also a change in the reaction mechanism (i.e., from a stepwise mechanism to a forced concerted pathway).
Alkaline hydrolysis of Y-substituted phenyl phenyl thionocarbonates: Effect of changing electrophilic center from C=O to C=S on reactivity and mechanism
Kim, Song-I,Park, Hey-Ran,Um, Ik-Hwan
scheme or table, p. 179 - 182 (2011/10/31)
Second-order rate constants (kOH-) have been measured spectrophotometrically for reactions of Y-substituted phenyl phenyl thionocarbonates (4a-i) with OH- in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 °C. The ksu
Study on the transesterification of methyl aryl phosphorothioates in methanol promoted by Cd(II), Mn(II), and a synthetic Pd(II) complex
Edwards, David R.,Neverov, Alexei A.,Brown, R. Stan
scheme or table, p. 1786 - 1797 (2011/04/23)
Methanol solutions containing Cd(II), Mn(II), and a palladacycle, (dimethanol bis(N,N-dimethylbenzylamine-2C,N)palladium(II) (3), are shown to promote the methanolytic transesterification of O-methyl O-4-nitrophenyl phosphorothioate (2b) at 25 °C with impressive rate accelerations of 10 6-1011 over the background methoxide promoted reaction. A detailed mechanistic investigation of the methanolytic cleavage of 2a-d having various leaving group aryl substitutions, and particularly the 4-nitrophenyl derivative (2b), catalyzed by Pd-complex 3 is presented. Plots of k obs versus palladacycle [3] demonstrate strong saturation binding to form 2b:3. Numerical fits of the kinetic data to a universal binding equation provide binding constants, Kb, and first order catalytic rate constants for the methanolysis reaction of the 2b:3 complex (kcat) which, when corrected for buffer effects, give corrected (kcat corr) rate constants. A sigmoidal shaped plot of log(k catcorr) versus sspH (in methanol) for the cleavage of 2b displays a broad sspH independent region from 5.6 ≥ sspH ≥ ～10 with a k minimum = (1.45 ± 0.24) × 10-2 s-1 and a [lyoxide] dependent wing plateauing above a kinetically determined sspKa of 12.71 ± 0.17 to give a k maximum = 7.1 ± 1.7 s-1. Bronsted plots were constructed for reaction of 2a-d at sspH 8.7 and 14.1, corresponding to reaction in the midpoints of the low and high s spH plateaus. The Bronsted coefficients (βLG) are computed as -0.01 ± 0.03 and -0.86 ± 0.004 at low and high sspH, respectively. In the low sspH plateau, and under conditions of saturating 3, a solvent deuterium kinetic isotope effect of kH/kD = 1.17 ± 0.08 is observed; activation parameters (ΔHPd? = 14.0 ± 0.6 kcal/mol and ΔSPd?= -20 ± 2 cal/mol?K) were obtained for the 3-catalyzed cleavage reaction of 2b. Possible mechanisms are discussed for the reactions catalyzed by 3 at low and high sspH. This catalytic system is shown to promote the methanolytic cleavage of O,O-dimethyl phosphorothioate in CD3OD, producing (CD3O)2P=O(S-) with a half time for reaction of 34 min.
